Fluorescence-lifetime measurements in monodispersed suspensions of polystyrene particles

Weak photonic band gap effect on the fluorescence lifetime in three-dimensional colloidal photonic crystals

“…The measured lifetimes for the three samples are 1 ϭ1.75 2 ϭ1.75 3 , and this significant variation was attributed to the inhibition of spontaneous emission, a pure PBG effect. However, later investigations in similar systems by Tong et al 5 and Megens et al 8 showed that electronic interaction between a dye molecule and a medium might account for a large fraction of the lifetime change observed. The controversy has continued until now.…”

“…[4][5][6][7][8][9] The observed lifetime is generally composed of two parts: one is due to the spontaneous emission of electronic excited states, the other is caused by other nonradiative internal processes in molecules. The corresponding decay rates can be denoted as ⌫ϭ1/ r and 1/ nr , respectively.…”

“…1 In the last decade, there appeared great interest in controlling the spontaneous emission rate via threedimensional ͑3D͒ photonic crystals, [2][3][4][5][6][7][8][9][10][11][12] which are artificial periodic materials. It was suggested that if the atomic transition frequency lies inside the photonic band gap ͑PBG͒, the spontaneous emission will be completely inhibited, 2 as there is no photon mode that can perturb atomic states.…”

“…[1][2][3][4][5][6][7][8][9] Martorell and Lawandy reported the first observation of inhibited spontaneous emission ͑SE͒ of dye molecules in dilute colloidal crystals composed of polystyrene microspheres in water. 4 They found a single exponential decay of the excited state and a variation of the fluorescence lifetime of 1.75 times.…”

“…However, Tong et al argued that this remarkable variation was caused mainly by electronic and chemical interactions between dye molecules and the medium, instead of a pure PBG effect. 5 Besides these complicated electronic and chemical interactions, other effects such as lattice defects, dislocations, and randomness inherent in the system may also influence the atom-field interaction, and, therefore, the SE. Thus it is very helpful to use accurate theoretical approaches to distinguish the pure PBG effect of an ideal photonic crystal on fluorescence lifetimes from other factors in observations made in a realistic photonic crystal.…”